Onychomycosis or tinea unguium (ringworm of the nails or fungal nail) is a chronic disease of the nails due to parasitic fungi. Onychomycosis can cause the nail to appear thickened and lusterless, and often causes nail discomfort. Also, the infected nail harbors a reservoir of pathogenic organisms which can spread to and reinfect other parts of the body, causing chronic diseases such as onychomycosis in other nails, athletes foot, toot dry skin and the like. Onychomycosis is prevalent throughout a large proportion of the population, with most of those afflicted from the ages of 40 years and older. To date, the United States Food and Drug Administration (FDA) has not approved any topical treatments for onychomycosis, either prescription or over-the-counter (OTC), due to the poor response of treatments evaluated. This poor response is partly because the nail is a difficult barrier for anti-fungal compounds to penetrate. In the Federal Register, Tuesday, Mar. 23, 1982, Part III Department of Health and Human Services, Food and Drug Administration, Topical Antifungal Drug Products for Over-the-Counter Human Use, Establishment of a Monograph reports: xe2x80x9cFungal infections of the . . . nails tend to be chronic. They respond poorly to topical therapy, partly because of the thickness of the nails . . . sites of infection provide inaccessible locations for fungi, thus drastically decreasing the penetration of topical antifungals. For this reason, OTC topical antifungals must be labeled that they are not effective for the treatment of ringworm of the . . . nails.xe2x80x9d The United States Food and Drug Administration recently re-affirmed its position in the ACTIONS: Final rule, Federal Register, Thursday, Sep. 2, 1993, 21 CFR Part 310, xe2x80x9cAntifungal, Anorectal, and Nail Biting and Thumbsucking Deterrent Drug Products; Rules.xe2x80x9d
The research by Jacob Brem, xe2x80x9cTreating Onychomycosis,xe2x80x9d The Lancet, Oct. 29, 1977, Vol 2., p. 937 demonstrates the extreme measures taken by one researcher to penetrate the nail: xe2x80x9c, . . . five or six holes are drilled in the nail plate, in the form of a crescent . . . Anaesthesia is not necessary. However, the introduction of the needle is felt when the nail bed is reached . . . The holes are enlarged by dipping a round toothpick in dichloroacetic acid and drilling through the hole in the nail. When the acid reaches the nail bed a burning sensation is felt . . . A week later, five or six new holes are drilled . . . If necessary, more holes could be drilled and further applications of acid could be given.xe2x80x9d
In a similar manner, the book, xe2x80x9cDiseases of the Nailxe2x80x9d by V. Pardo-Castello, Thomas Books, Baltimore, Maryland, (1936), pp. 22-40 describes several treatments for onychomycosis, including the following: xe2x80x9cCraik (43) has reported two cases treated with success by means of daily applications of a solution of 4 grams of salicylic acid in 45 c.c. of methylated spirit, after thoroughly scraping the nail. The cited reference, R.Craik, xe2x80x9cA Simple Treatment of Ringworm of the Nailsxe2x80x9d, Brit. M. J. February 1920, p. 185 describes a procedure wherein a lotion containing salicylic acid was xe2x80x9c. . . to be painted on after scraping [the finger nail] every night, and without scraping every morning, and to be used for three months or longer.xe2x80x9d Scraping a finger nail each day for three months or more has effect of thinning or completely removing the nail plate.
Avulsion or surgical approaches for treating onychomycosis have also been used. Infected nails are treated by surgically or chemically removing the nail and treating the exposed nailbed with topical antifungals. These treatments must be continuted until the nail grows out, typically 6 months or more. Although the surgical approach generally results in cure rates significantly higher than those reported for topical treatments, most patients dislike undergoing surgery, which can result in permanent nail loss.
International Application WO 88/06884 teaches treating nail mycosis with a pharmaceutically effective amount of a topical antimycotic such as an imidazole compound, optionally with an antiseptic as exemplified using about 5% salicylic acid in a liquid preparation. There is no suggestion in this reference that salicylic acid, by itself, can serve as the antimycotic active ingredient. Nor does this reference suggest the unexpected and surprising discovery that salicylic acid, applied topically, will penetrate into the nail and exert an antifungal effect, in the absence of an imidazole antimycotic agent.
U.S. Pat. No. 5,004,599 to Scher teaches that tretinoin, also known as all-trans retinoic acid or Vitamin A acid, can promote growth of the nail unit, for purposes of improving cosmetic appearance. However, this reference offers no hint or suggestion of using tretinoin to treat a fungal nail disease such as onychomycosis. To date, the United States Food and Drug Administration (FDA) has not approved any topical treatments for onychomycosis, either prescription or over-the-counter (OTC).
Clearly, there is a need to provide an effective method for treating onychomycosis in which an active ingredient can be applied topically to an afflicted nail, without the need to drill holes in the nail, scrape the nail daily for three months or more and/or avulse the nail. There is also a need to provide a method for treating onychomycosis through use of a medicated device or a film-forming liquid preparation which enables the salicylic acid to remain in contact with the nail, thus facilitating its penetration into the nail.
The present invention is directed toward the use of salicylic acid or a salt, ester, or mixture thereof for the manufacture of a medicament to treat onychomycosis (fungal nail) by topical application to a nail, without drilling holes in the nail or periodic scraping of the nail and in the absence of an imidazole antimycotic compound. The salicylic acid can be in a medicament which is either a plaster preparation or a liquid preparation.
In another embodiment, the present invention is directed toward a medicament for treating onychomycosis without drilling holes in the nail or periodic scraping of the nail and in the absence of an imidazole antimycotic compound. The medicament comprises salicylic acid, or a salt, ester, or mixture thereof for topical application to a nail. Optionally, the medicament may also contain retinoid compound for promoting nail growth. Salicylic acid and retinoid may also be combined in a kit comprising in separate containers in a single package, salicylic acid, or a salt, ester, or mixture thereof and a retinoid compound. In the kit, preferably salicylic acid and the retinoid are in separate containers for liquid preparations.
In yet another embodiment, the present invention is directed towards a method for treating onychomycosis of an afflicted nail of a mammal without drilling holes in the nail or periodic scraping of the nail and in the absence of an imidazole antimycotic compound, by topically administering, either:
i) a medicated device comprising an active ingredient which is salicylic acid or a salt, ester or mixture thereof in a plaster preparation and the salicylic acid is present in the plaster preparation in an amount effective to treat onychomycosis; or
ii) a liquid preparation comprising an active ingredient which is salicylic acid or a salt, ester or mixture thereof in a film-forming liquid vehicle, and the salicylic acid is present in the liquid preparation in an amount in an amount effective to treat onychomycois.
Optionally, the method can be practiced by combining a retinoid compound with the salicylic acid in the medicated device or liquid preparation.
Preferably the salicylic acid is employed in a plaster preparation using self-adhesive rubber or acrylic-based plaster vehicle.
The present invention has the advantage of providing an easy-to-use method for treating onychomycosis in which the afflicted nail can be treated directly, as compared to indirect or systemic methods utilizing oral antifungal agents. By directly treating the afflicted nail, fewer side effects can be expected compared with oral antifungal agents. The present method can also provide for convenient, continuous delivery of the active ingredient (ie. salicylic acid) over the treatment period. When a medicated device is employed, the method can provide further advantages in that: i) a medicated device made of a plaster and/or its carrier can be constructed to occlude and hydrate the nail for assisting delivery of the active ingredient from the plaster and promote penetration into the nail, due in part, to the increased permeability of the nail; ii) a medicated device can retain the active ingredient in place despite rubbing or scraping of the medicated device against hosiery or the shoe; iii) a medicated device has little or no odors compared with solvent-based systems; iv) a medicated device can be easily applied by placing it in contact with a nail, and can also be easily removed by peeling it off when finished; and v) a medicated device can theoretically hold greater amounts of the active ingredient since it can be made thicker than a solvent-based lacquer application.